Editors’ Choice — Featured Classic Papers

Below are select classic papers from past issues, chosen by the editors, along with commentary on what makes these classics. The Journal of Marine Research continues to serve the academic oceanographic community by publishing papers vital to marine research, in the long and rich tradition of the Sears Foundation for Marine Research at Yale University. Each paper below is available as a free downloadable file.

On the mutual adjustment of pressure and velocity distributions in certain simple current systems

On the mutual adjustment of pressure and velocity distributions in certain simple current systems, II

By Carl-Gustaf Rossby

These are the original geostrophic adjustment papers. Rossby starts out by asking what, if anything, limits the ability for a flow to be in geostrophic balance (to precisely follow pressure contours on a rotating planet). This topic is now a classroom standard, but we often forget how insightful the original papers are. Three interesting aspects of this paper are:

—Rossby introduces the seemingly ubiquitous “radius of deformation,” a length scale (given by the long gravity wave speed divided by the Coriolis parameter) that crops up in virtually any problem involving a horizontally divergent flow on a rotating planet. It is instructive to read how Rossby chose the name.

—Rossby points out that momentum will be transferred downward in a stratified ocean, so that we should never expect the deep ocean to be quiescent. This more than a decade before the landmark Swallow and Crease experiment demonstrated this in the real ocean.

—The papers foreshadow the yet-to-be-discovered theory of baroclinic instability, which, in nature, limits how strong a geostrophically balanced vertical shear can become and, in the process, creates weather in the atmosphere.

C.-G. Rossby was one of the few ocean scientists who made the cover of TimeMagazine. This paper is a classic, still enlightening almost 75 years later. —Ken Brink, Editor

A bathythermograph

By A.F. Spilhaus

In this classic, Athelstan Spilhaus reports on his progress on a prototype of the mechanical bathythermograph, a project that C.-G. Rossby encouraged him to pursue. Although now most often seen in museums or on movie sets (they look a bit like rockets), bathythermographs were extremely influential from the later 1930s into the 1950s. These remarkable, durable instruments allowed continuous traces of temperature versus depth (previously measured as bottle temperatures at 50 meter separations), and so opened up an entirely new vision of what ocean thermal structure actually looks like. Spilhaus provides some actual data, but gives no interpretation for these entirely novel measurements.

The bathythermograph proved to be extremely useful for submarine warfare during the Second World War, when it became understood that the sharp thermal structures observed with a bathythermograph strongly influenced sound propagation and its diurnal variability in the ocean.

Spilhaus had a distinguished academic career at Woods Hole Oceanographic Institution and at the University of Minnesota. Many of us remember his weekly newspaper comic strip “Our New Age,” which introduced scientific concepts to the general public. —Ken Brink, Editor

On the oxidation of organic matter in marine sediments by bacteria

By Selman A. Waksman and Margaret Hotchkiss

Selman Waksman is best known for his work on natural antibiotics, for which he originated the term and received a Nobel Prize. However, he and co-workers also extensively investigated soil microbes and their interactions with biogeochemical processes and elemental cycling.

Although perhaps long forgotten, in this contribution from 1937, Waksman and his close associate, Margaret Hotchkiss, documented the biological availability and reactivity of marine sedimentary organic matter in different types of sediment, as a function of initial burial depth in deposits, and variation with bathymetric depth in the North Atlantic. They used simple serial incubations with oxygen to measure reactivity and decomposition behavior of sedimentary organic matter, an approach that remains in use to this day. They also deduced fundamental concepts that we now commonly incorporate into theories and that underlie sophisticated models of marine carbon and nitrogen cycling, such as the progressive oxidation and diagenetic loss of reactive components during transport into sedimentary deposits or away from surface water and continental boundary sources. —Robert C. Aller, Associate Editor

On the process of upwelling

By H.U. Sverdrup

Although Harold Sverdrup is now probably best known for his work on basin-scale ocean circulation, his interests were remarkably diverse, and included continental shelf processes. As a coastal oceanographer, I can’t resist highlighting this contribution to the coastal upwelling literature. A relatively simple data set is exploited here, consisting of cross-shelf sections taken near Point Conception, California.

Building on Vagn Walfrid Ekman’s conceptual framework, Sverdrup uses these data to show its qualitative consistency with available wind data, and goes on to diagram a cross-shelf vertical circulation pattern. This paradigm, which neglects alongshore variability, dominated oceanographic thought into the early 1970s—a strikingly long reign.

This was not Sverdrup’s only excursion into this part of the ocean. His 1941 paper with Richard Fleming (“The waters off the coast of southern California. March to July 1937.” Bulletin of the Scripps Institution of Oceanography) presents a remarkable set of three-dimensional observations in the same general region. These measurements reveal eddies and jets that show the considerable three-dimensionality of the system.

This very insightful and informative work was apparently largely forgotten until the 1970s, when satellite sea surface temperature observations started to reveal the same sorts of features. This new, exciting data led eventually to a recognition of Sverdrup’s earlier accomplishments on this subject. —Ken Brink, Editor

Relation between variations in the intensity of the zonal circulation of the atmosphere and the displacements of the semi-permanent centers of action

By C.-G. Rossby and Collaborators

Here Carl-Gustav Rossby, motivated by observations of weather patterns that move upstream relative to the dominant mid-latitude eastward wind flow, formulates a completely novel linearized theory to account for the tendency for large-scale disturbances to move westward and smaller-scale disturbances to move eastward relative to the winds.

We now recognize this solution as the Rossby wave. Although the expressions here describing these waves look foreign to us now, this is partly a matter of notation and partly that Rossby only considered waves propagating strictly east- west, with no possible meridional propagation. Along the way, he introduces and rationalizes the now ubiquitous beta-plane—“β”—a term compactly representing the latitudinal variation of effective rotation rate—that is, the effect of a spherical Earth.

Both Rossby waves and the beta-plane are well-used tools known to anyone studying ocean or atmospheric dynamics. Rossby’s understanding of these two related effects has since opened countless doors in oceanographic research. —Ken Brink, Editor

The relationship of vertical turbulence and spring diatom flowerings

By Gordon A. Riley

The dynamics of spring blooms of phytoplankton in temperate waters are usually associated with H.U. Sverdrup’s 1953 “critical depth” model. However, more than a decade earlier, Gordon Riley published a statistical and mechanistic analysis of data he had gathered over two spring “flowerings” on Georges Bank.

In this work, Riley laid out the foundations that were eventually encoded in Sverdrup’s model. Riley’s data showed that increasing vertical stratification in the spring decreased thickness of the “turbulent zone” through which phytoplankton were mixed. This reduction in vertical mixing allowed net positive phytoplankton growth—decoupled from zooplankton grazing or sinking losses—leading to a spring bloom.

Riley formulated his hypothesis as a rate model, in which the photosynthetic rate was scaled by the ratio of the thickness of the euphotic zone to the thickness of the “zone of vertical turbulence.” Though his model was not as mathematically elegant as Sverdrup’s, Riley went on to quantify all the parameters of his model, showing that during the bloom, the mean phytoplankton growth rate increased as the turbulent mixing layer thickness decreased.

Riley’s remarkably thorough, thoughtful, and careful analysis of the dynamic underpinnings of the spring bloom is underappreciated, and worthy of inclusion in any discussion of the dynamics of spring blooms. Published only five years after receiving his doctorate, Riley’s 1942 paper is an impressive contribution to our understanding of physical-biological interactions in the ocean. —Peter Franks, Associate Editor

The influence of deposit-feeding organisms on sediment stability and community trophic structure

By Donald C. Rhoads and David K. Young

This seminal paper by Donald Rhoads and David Young was a highly creative, interdisciplinary break from the standards of the time. It brought a new focus onto how benthic organisms modify sediment properties, potentially mediating interactions with other species, structuring community distributions, and governing coupling between sedimentary deposits and overlying waters.

Classical studies of marine benthic communities had traditionally examined species distributions and their statistical correlations with sediment type with little consideration of interactions of fauna with the sedimentary environment or the consequences of biological modifications of this environment. For example, it was widely recognized that many deposit-feeding benthos were often segregated from suspension feeders into muds and sands, respectively, but interpretations of why centered almost entirely, although not exclusively, on food resources.

The pioneering work by Rhoads and Young is a remarkable synthesis of physical and biological field observations, deceptively simple experiments, autecology, and clear deductive reasoning. They proposed a novel view and conceptual theory of ecological relationships in sedimentary systems: trophic group amensalism. In doing so, they also introduced a new technology—sediment profile imaging, which spawned use of sophisticated SPI cameras to rapidly assess benthic communities and sediment properties. This opened the way for other innovative approaches, such as planar imaging sensors.

Rhoads and Young fomented a conceptual revolution that transformed perspectives and stimulated a wide-range of later research on recent and ancient sedimentary environments, including ecological, sediment transport, and biogeochemical processes. —Robert C. Aller, Associate Editor

On properties of seawater, defined by temperature, salinity and pressure

By George Veronis

A classical, and highly productive, approach to studying hydrographic data in the ocean is to use T–S (Temperature–Salinity) analysis. This is a convenient methodology that allows definition of water mass types and quantification of mixing. Information about temperature, salinity and pressure (depth) can further be used to calculate the water’s density.

The important insight of this contribution is the recognition that the same information used to calculate density can also be used to calculate a quantity, called τ here, that is orthogonal to density in T–S space. Using the traditional assumption that water preferentially moves along density surfaces, τ is then a remarkably useful tag for water parcels as they move and are mixed laterally.

It did not take long for the Veronis τ to receive the much catchier name “spiciness” (see Walter Munk’s chapter “Internal waves and small-scale processes,” in The Evolution of Physical Oceanography, edited by B.A Warren and C. Wunsch, MIT Press, 1981) and the quantity has since become a standard tool in the analysis of ocean hydrographic data. —Ken Brink, Editor

Deepening of the wind-mixed layer

By Pearn P. Niiler

One of the classic and very important problems in physical oceanography is understanding the behavior of the surface mixed layer. This uppermost 10 to 100 meters of the ocean is the domain most directly affected by atmospheric forcing, and it is critically important for biological processes, because it is often the habitat for phytoplankton.

Before Niiler’s paper, several important studies had each emphasized different aspects of how the mixed layer behaves, such as the effect of surface cooling or of shear across the bottom of the mixed layer. What makes this paper special is that it pulls together the most important threads up to that time, and creates an inclusive synthesis that shows under what circumstances the different specialized concepts apply. Although this paper has since been superseded, most notably by the 1986 paper by Price, Weller and Pinkel (Journal of Geophysical Research 91(C7):8411–8427), it still stands out in terms of the clarity with which it explains the different stages and processes involved. —Ken Brink, Editor